The RENDER extension adds a new set of drawing primitives which effectively represent a replacement of the drawing routines in the core protocol, redesigned based on the needs of more modern clients. It adds long-desired features such as subpixel positioning, alpha compositing, direct specification of colors, and multicolored or animated cursors. On the other hand, it omits features that are no longer commonly used: wide lines, arbitrary polygons (only triangles and horizontally-aligned trapezoids are supported), ellipses, bitwise rendering operations, and server-side fonts (in favor of "glyphs" that are rendered on the client side and transmitted once).

As of this writing (early 2004), the specification and implementation both have rough edges, but there are relatively few alternatives for offloading fancy graphics processing to the server, as is necessary over slow links or if the client is written in a slow language. Another possibility you might consider is the 2D subset of OpenGL, though it doesn't yet have an X11::Protocol-compatible interface.